Long-range antiferromagnetic interactions in ZnFe2O4 and CdFe2O4

TL;DR

This study uses first-principles density functional theory to quantify long-range antiferromagnetic Fe-Fe interactions in zinc and cadmium ferrites, revealing unexpectedly strong third-neighbour interactions.

Contribution

It provides the first quantitative analysis of Fe-Fe interactions in these geometrically frustrated antiferromagnetic systems using DFT methods.

Findings

All Fe-Fe interactions up to third neighbours are antiferromagnetic.

Third-neighbour interactions are stronger than second-neighbour interactions.

Third-neighbour interactions are comparable in magnitude to first-neighbour interactions.

Abstract

For the first time, the Fe-Fe interactions in the geometrically frustrated antiferromagnetic systems of zinc and cadmium ferrites are determined quantitatively by the first-principles methods of density functional theory. Both the generalized gradient approximation (GGA) as well as GGA plus the onesite Coulomb interaction (GGA+U) are considered for the exchange-correlation energy functional. The interactions up to third neighbours are found to be all antiferromagnetic for both materials, regardless of which approximation scheme (GGA or GGA+U) is used. Surprisingly, the thirdneighbour interactions are estimated to be much stronger than the second-neighbour interactions and on the same order in magnitude as the first-neighbour interactions.